WASHINGTON — Just two days after quitting the presidential race, former pizza exec Herman Cain is reportedly set to endorse new front-runner Newt Gingrich today.

Cain, who dropped out after a woman claimed to have had a 13-year affair with the married businessman, will play king-maker to the former House speaker at a 2 p.m. press conference in Manhattan, Atlanta Fox affiliate WAGA-TV said last night.

The endorsement comes as Cain’s spectacular crash has left Gingrich firmly perched atop the GOP presidential field in Iowa.

Even Robert Gibbs, a top adviser to President Obama’s re-election campaign, admitted yesterday that the rise of Gingrich is “for real.”

“I have got tell you, I think a lot of people inside the Beltway and outside the Beltway woke up today to a very different political environment and one in which Newt Gingrich is very much for real,” Gibbs told CBS’s “Face the Nation.”

Still, he cautioned that a brutal contest lies ahead and “there’s great skepticism” that Gingrich will be the nominee.

According to The Des Moines Register’s newest Iowa Poll, Gingrich leads the GOP pack with 25 percent, followed by Texas Rep. Ron Paul with 18 and former Massachusetts Gov. Mitt Romney, who dropped to third with 16.

Cain, who had been the front-runner, with 23 percent, plummeted to a paltry 8 percent.

That left him tied with Minnesota Rep. Michele Bachmann in the survey of likely Republican participants in the Hawkeye State’s first-in-the-nation nominating contest, on Jan. 3.

Gingrich’s surge couldn’t have come at a better time for him.

But Romney is polling stronger than him in New Hampshire, host of the first primary, on Jan. 10.

Today, Gingrich heads to a New York City meeting with Donald Trump, making him the fifth GOP contender to make the pilgrimage to Trump Tower in search of an endorsement.

Paul is skipping a Dec. 27 debate in Iowa because it will be moderated by Trump — whom he called “clown-like.”